The present invention relates to pressure sensors. In particular, the invention relates to capacitive pressure sensors having cell body and diaphragm components made of sintered ceramics fired to near net shape to minimize expensive machining operations.
Capacitive pressure sensors have found widespread use in industrial process, aerospace, and other control and monitoring systems. Capacitive pressure sensing cells can be configured to sense absolute pressure, gauge pressure, differential pressure, or combinations of those pressures.
In some cases, capacitive pressure sensors are used to measure pressure of fluids that may be corrosive to metal parts of the sensor. One technique used to address this issue is to separate the pressure sensor from the process fluid using an isolation diaphragm. An oil fill then couples the pressure sensor to the isolation diaphragm, so that pressure applied to the isolation diaphragm is transferred through the oil fill to the diaphragm of the capacitive pressure sensor. This isolation technique, however, can introduce errors in pressure measurements.
Capacitive pressure sensors have been fabricated from a variety of materials, such as metal, glass, sapphire, and silicon. There is a continuing need for improvements to capacitive pressure sensors (and in particular differential pressure sensors) to provide smaller sensors, which use lower oil fill volumes, and which are less expensive to fabricate.